Field of the Invention
The present invention relates to an image display apparatus having a display device and an input device integrated together, allowing touch-input. More specifically, the present invention relates to a touch drawing display apparatus that has functions of drawing operation and other operation regarding touch operations, and operation method thereof, as well as to an image display apparatus switching images page by page by touching and sliding images with a plurality of fingers and the like and a controller for the display apparatus.
Description of the Background Art
As an image display apparatus allowing touch-input, a so-called electronic blackboard having a display device with a large screen, allowing drawing of an image or other processes upon detection of touching of the display device by the user has been known. The electronic blackboard is useful when summarizing opinions of participants or finding a preferable solution to a problem, for example, at a meeting. Electronic blackboards having various configurations have come to be practically used, and one configured as a computer system having a combination of a display device with a large display screen and an input device for detecting two-dimensional position coordinates such as a touch-panel has been used.
Generally, an electronic blackboard apparatus successively reads pieces of information related to position coordinates designated by a pen or a finger and pieces of information related to amount of movement, and displays a track of inputs on the display device based on the read pieces of information. Consequently, the apparatus can realize operations as an electronic blackboard such as handwriting input.
Regarding the touch operation, Japanese Patent Laying-Open No. 6-175776 (hereinafter denoted as '776 Reference) discloses a projection type presentation device allowing drawing on a displayed screen image using touch operation. There is a problem that recognition of an original image becomes difficult when writing is repeated on the same screen image. In order to solve this problem, in the device disclosed in this reference, drawing is done while touch operation is continued in an image forming area, and when the touch operation in the image forming area once ends and then a touch operation in the image forming area is detected next, the former image is automatically deleted.
If a specific function other than drawing is allocated to a touch operation different from a simple touch operation for drawing in an electronic blackboard, while an image is being drawn in a drawing mode, it takes some time until a touch operation is determined to be the one for executing the specific function. Typically in an electronic blackboard, drawing is done immediately after the touching, so as not to cause any time lag between the touch operation and drawing. Any time lag is stressful for the user. Such a configuration sometimes leads to an erroneous drawing not intended by the user. By way of example, it is often the case that an operation of flicking with multi-touch (touching a plurality of points simultaneously) is allocated to an operation of scrolling screen images. In such a situation, if the user is drawing images with single-touch operation (touching one point at a time) and then makes a multi-touch flick operation for scrolling screen images, it is necessary to monitor the tracks of touched points for a prescribed time period to determine that it is a flick operation. As the image is drawn immediately in response to the touching to avoid any stress to the user, it follows that an erroneous image not intended by the user have been drawn by the time when the operation is determined to be the multi-touch flick operation. While the image with the erroneous drawing disappears from the screen image when the screen images are scrolled, drawing information containing the erroneous drawing is stored as it is. Therefore, when scrolled back to the original screen image, the erroneous drawing again appears on the screen image. When printing is done, similarly, the erroneous drawing is also printed.
This problem is not limited to the electronic blackboard, and it occurs in display devices allowing display of images drawn by touching, such as tablet-type terminals. This problem cannot be solved by the technique disclosed in '776 Reference.
Advantages of an electronic blackboard include that it is possible to display or write (draw) images separately on a plurality of screen images. Each unit of display of such images is referred to as a “page” as an analogy to a book.
In an electronic blackboard allowing display of a plurality of pages of images, how to switch pages easily is an issue. The easiest method may be to provide a button for switching pages on the screen image. This method, however, is problematic particularly when the screen image is large, as it becomes difficult for the user to press the button depending on the position of the user.
In view of the foregoing, other than the method using the button, a method of switching the screen images by touching the screen image with a finger and sliding the same is proposed. Here, if it is too simple, the operation would be the same as the usual drawing operation. Therefore, in order to distinguish the two different operations, Japanese Patent Laying-Open No. 11-102274 (hereinafter referred to as '274 Reference) proposes a device in which the screen image is switched if the screen image is touched by a plurality of fingers and the like (a so-called multi-touch) and the plurality of touched positions are slid by more than a prescribed value in the same direction.
Japanese Patent Laying-Open Nos. 8-76926 (hereinafter referred to as '926 Reference) and 9-231004 (hereinafter referred to as '004 Reference) disclose methods as further development of the idea described above. According to the method described in '926 Reference, when an operation of touching and sliding is done, a page is turned, and the number of pages turned at one time is changed depending on the number of touching fingers (the number of touched positions). According to the method disclosed in '004 Reference, scrolling of images, turning of pages and moving of cursors are executed in accordance with the movement and number of fingers touching the display screen surface.
According to the techniques disclosed in '274, '926 and '004 References described above, it is possible to turn pages by the simple operation of touching and sliding. There is still a problem to be solved. Specifically, pages may be turned erroneously while normal input is being done. Particularly when input is being done using a finger, it is possible that a finger other than the finger used for input happens to touch the screen surface and is detected as the multi-touch slide input and, as a result, a page is turned unintentionally. Therefore, a mechanism that can prevent unintended turning of a page even when such an erroneous input is made has been desired. Further, a mechanism that allows the user to easily understand what manner of input is necessary to turn a page is also necessary.